1. Field of the Invention
The present invention relates to a rotary electric machine including a rotor in which permanent magnets are housed in a rotor core thereof.
2. Description of the Related Art
In a conventional synchronous motor, a rotor includes permanent magnets which are disposed around a rotation shaft at substantially regular intervals, and stacked core members which are disposed between the permanent magnets and form magnetic poles, respectively. The stacked core members are formed by mutually stacking and combining a large number of thin plate core pieces and integral thin plate cores which are made of a magnetic material. The integral thin plate cores include thin plate core piece portions having the same polarity applied thereto and having the same shape as that of the thin plate core piece, and connection portions which mutually connect these thin plate core piece portions. When the large number of thin plate core pieces and the integral thin plate cores are integrally combined by caulking, the respective stacked core members are mutually connected at relative positions at the time of completing assembly, in which placement spaces for the permanent magnets are provided between adjacent stacked core members. Thus, an integral stacked rotor core is formed.
In general, in a rotary electric machine including a rotor in which permanent magnets are housed in a rotor core thereof, output of the rotary electric machine is lowered by a leakage flux between the magnetic poles having different polarities, which flows within the rotor and does not contribute to torque. In the conventional synchronous motor, the magnetic poles having different polarities are prevented from being short-circuited at the connection portion so as to reduce the leakage flux by using the integral thin plate cores, in which only the thin plate core piece portions having the same polarity applied thereto are connected to one another via the connection portion.
Moreover, in the conventional synchronous motor, layers of only the thin plate core pieces including no connection portion are disposed to be stacked between the integral thin plate core forming the magnetic pole of one polarity and the integral thin plate core forming the magnetic pole of the other polarity so that the three dimensional leakage flux is suppressed (for example, see Japanese Patent Application Laid-open No. Hei 6-245451).
In the conventional synchronous motor, when the rotation shaft is a magnetic body, a leakage flux is generated via the rotation shaft even when no short circuit magnetic path exists between the stacked rotor core layers. A leakage flux amount of the respective magnetic poles can be equalized in the entire rotor to some extent by applying rotational stacking, but there still exist, in the respective magnetic poles, a difference of a leakage flux amount in the rotation axis direction, and a difference of a leakage flux amount on the same stack plane. Due to these differences of the leakage flux amounts, non-uniformity of the magnetic flux amount from the respective magnetic poles contributing to the torque occurs, which leads to a problem in that vibrations occur in the electric motor due to rotation fluctuation and unbalance of force at the rotor.